This ticket is too broad, and it won't be possible to ever consider it fixed.

Please open separate tickets for any feature you'd like to see. I can see a number of tickets here:

'required' attribute

placeholder attribute

EmailInput widget

UrlInput widget etc.

Please note that we have a strong backwards compatibility commitment, so we won't add new features (or at least have them enabled by default) if they break things for older browsers. This is another reason to split this ticket into multiple tickets, so the problems with one won't hold up the others being added.

Can I also note that at least some of these are simple, easy new features (feel free to add the 'Easy pickings' flag to you new tickets), and such things are especially good candidates for you to implement. Core developers are going to spend their time doing things that other members of the community can't do, so nice patches with docs and tests will certainly be welcomed, but we are unlikely to write them :-)